The present invention relates generally to a video signal processing apparatus and, more particularly, to a recording format discriminating apparatus for use in a helical scan VTR device capable of discriminating between an analog recording format and a digital recording format of signals recorded on a recording medium.
With recent technological advances, it has become possible record and reproduce video signals on small-size recording media (or cassette) of a same shape, either in analog format or digital format. Consequently, configuring an 8 mm-format recording/reproducing apparatus such that changeover is made between drum rotational speeds and between capstan speeds to accomplish analog recording/reproduction and digital recording/reproduction with the same apparatus increases the merits of the apparatus. However, this requires to determine at reproduction whether a recording medium (or a cassette) is recorded in analog format or digital format to automatically select a drum rotational speed or capstan speed and a reproduction frequency band that match the detected recording format.
For discrimination of recording formats, a method is proposed in which the presence or absence of a spectrum point of an FM luminance signal (YFM) and a superimposed signal unique to the 8 mm and Hi-8 mm formats is determined. However, it is generally difficult to make the discrimination only by a particular spectrum point because, in digital format recording, a wide band spectrum is provided to effectively use the entire band of electromagnetic conversion system.
Conventionally, in the reproduction of a signal from a magnetic tape for example, the head and the rotary transformer of a recording/reproducing apparatus are made optimum in accordance with the signal format in electromagnetic conversion required for the reproduction of that signal.
Therefore, as with a wide-band digital signal and a narrow-band digital signal for example, when reproducing signals in electromagnetic conversion having different required band characteristics, the reproducing head and the rotary transformer dedicated to the format of each of digital and analog signals are used. It should be noted that the rotary transformer in this case is made multi-channel for each of the above-mentioned digital and analog signals.
As described, when a configuration in which both analog and digital recording/reproducing operations are enabled on a same video tape recorder (VTR) is considered, it is required to automatically discriminate at reproduction the recording format of a signal recorded on the recording medium.
It is therefore an object of the present invention to realize a recording format discriminating apparatus for use on VTRs that discriminates comparatively easily and reliably the recording format of a signal recorded on recording medium.
In carrying out the invention and according to one aspect thereof, there is provided a recording format discriminating apparatus for use on a video tape recorder capable of reproducing a signal recorded on a recording medium in a digital recording format or an analog recording format by one and same head rotary system or a plurality of head rotary systems dedicated to analog recording and digital recording respectively. The apparatus comprises: an amplifier, having a capability of automatically controlling a gain of a signal reproduced by one of the head rotary systems, for amplifying the signal to a predetermined level; a first band extracting circuit for extracting a particular narrow frequency band from the amplified signal; a first comparator and detector for detecting by amplification an output of the first band extracting circuit and comparing the detected output with a first reference value; a second comparator and detector for integrating and holding the comparison result output of the first comparator and detector and then comparing the integrated output with a second reference value; and a recording format discriminating circuit for discriminating the recording format of the signal recorded on the recording medium from the comparison result output of the second comparator and detector.
As described above, if, for the purpose of reproducing signals having different required band characteristics in electromagnetic conversion, a plurality of reproduction heads dedicated to these signals or multi-channel rotary transformers are disposed, the material and design costs increases and the scale of the circuit configuration grows. For example, if the reproduction heads dedicated to digital signal and analog signal and corresponding rotary transformers are disposed, the cost and the scale of configuration become twice or more as high as the configuration in which means are provided only for one signal format.
In addition, a digital recording/reproducing apparatus having upward compatibility (in this case, the upward capability is digital recording/reproducing) that allows only the reproduction of conventional analog signals while normally recording and reproducing digital signals is configured for example, the above-mentioned cost increase and the growth of configurational scale cause a significant burden for the manufacturer.
On the other hand, if signals having different required band characteristics in electromagnetic conversion are reproduced by use of one magnetic head and one rotary transformer, for example by use of a magnetic head and a rotary transformer each dedicated to a certain signal format, a signal having a different signal format is reproduced with a deteriorated C/N (carrier to noise) ratio. Obviously, use of a magnetic head and a rotary transformer optimized to no signal format deteriorates C/N at reproduction of any signal.
It is therefore another object of the present invention to provide a signal reproducing apparatus and a signal reproducing method for reproducing in a good condition (namely, with an improved C/N ratio) signals having different required band characteristics in electromagnetic conversion by use of one magnetic head and one rotary transformer and preventing the cost and configurational scale from being increased.
In carrying out the invention and according to another aspect thereof, there is provided a signal reproducing apparatus for at least reproducing signals having different band characteristics in electromagnetic conversion from a magnetic recording medium by use of one magnetic head and one rotary transformer, wherein a resonance frequency determined by an equivalent inductance and a resonance capacitance of the magnetic head and the rotary transformer is varied or selected according to formats of signals having different band characteristics in electromagnetic conversion.
According to the present invention, in the case where such signals in electromagnetic conversion having different required band characteristics as a digital signal and an analog signal for example are reproduced by use of one same magnetic head and one same rotary transformer, the C/N ratio and amplitude characteristics in each band can be optimized by varying or selecting resonance frequencies and damping quantities according to the signal formats of these signals.